Mining System for Thick Coal Seams in the Tom-Usa District of Kuzbass

V. V. Proskurin, V. S. Evseev, G. E. Posokhov

The Tom-Usa district occupies the southeastern margin of the Kuznetsk coal basin. In terms of coal content and reserves of high-quality coking coals, it is considered one of the largest in the world.

Within the Tom-Usa district, two hard-coal deposits are distinguished: the Tomskoye and the Olzherasskoye. The coal seams of these deposits have considerable thickness and are distinguished by the relative persistence of their occurrence elements.

At present, the most explored part of the district is the South Olzherassky area. Here 11 workable coal seams have been found, of which three seams—III, IV—V, and VI—have a thickness from 6 to 10.5 m (Fig. 1). About 50% of the deposit’s coal reserves are concentrated in these thick seams. The seams occur at an angle of 7—18°. The coals of the seams possess high mechanical strength. All coal seams are prone to spontaneous combustion and are hazardous with respect to gas (methane) and dust.

Industrial development of the Tom-Usa district began recently. The first mine, “Tom-Usinskaya 1—2,” was put into operation in 1953. The accumulated experience in mining thick coal seams has revealed a number of difficulties, caused mainly by unusual mining-and-geological conditions and by the absence of a rational mining system.

Until recently, only one mining system had been used on the thick seams of the “Tom-Usinskaya 1—2” mine—inclined slices with caving of the roof. Over three years of using this mining system at the mine, extremely low technical-and-economic indicators were obtained.

Average monthly output of the longwall face, t
    in the first slice . . . . . . . . . . . . . . . . . . . . . . 3820—5650;
    in the second slice . . . . . . . . . . . . . . . . . . . . . 3080—5350;
    in the third slice . . . . . . . . . . . . . . . . . . . . . . . 1730;
    in the fourth slice . . . . . . . . . . . . . . . . . . . . . . 2020;
average monthly advance of the longwall face, m . . . . . . . 8—16;
consumption of timber materials per 1000 t of coal mined, m³ . . 80—106;
cost of 1 t of coal
    (wages, materials, depreciation), rub. . . . . . . . . . . . 31.5—46;
coal losses in the lower slice, % . . . . . . . . . . . . . . . . 27—40.

The low technical-and-economic indicators are due to the laboriousness of roof-control operations. The roof of seams III and IV—V is represented by strong sandstones of great thickness. It caves זיך

Fig. 1. Geological cross section along exploration line II of the South Olzherassky area of the Tom-Usa district of Kuzbass.

Visible labels in the figure: 215 (15); 230 (8); 210 (10); Seam III; Seam IV–V; Seam VI; Seam VII-a; Seam VIII–IX; Seam XI; Seam XII–XIII; Seam XIII; Seam XV; Seam XVI.

with large blocks. The rocks, even after a long period, do not cave. This circumstance often brings longwalls into an emergency condition, especially in the lower-lying seams. In 1956 alone, at the Tom-Usinskaya 1–2 mine, 90 longwall falls were recorded. In individual sections there were hang-ups of the main-roof rocks. All this led to prolonged stoppages of the stoping faces.

In recent years several new mining systems have been proposed for the thick seams of the Tom-Usa district. Some of them (a mining system with a flexible shield cover, a mining system with movable enclosing supports under the protection of a flexible cover (KTU), etc.) are undergoing industrial trials at the Tom-Usinskaya 1–2 mine. The mining system proposed in the present article has been accepted for testing under production conditions. The authors have called it a mining system in strips along the dip with a yielding concrete support.

The essence of the mining system

The essence of the mining system in strips along the dip with yielding concrete support is that, within the limits of the extraction field, a thick flat-lying seam is prepared for stoping by workings driven through the coal at the floor and roof of the seam (Fig. 2). From these workings, niches are cut for erecting the concrete support, and from them, normal to the seam roof, raises are driven, which are subsequently filled with concrete. After the concrete has hardened sufficiently, wooden cribs are laid on the upper platforms of the concrete supports (Fig. 2). A support of this construction, owing to the yielding capacity of the wooden cribs, can take the rock pressure together with the coal mass during the period when the concrete supports are in the coal barriers.

It is proposed to extract the coal within the limits of the extraction field in strips along the dip, with the use of drilling-and-blasting operations and partial hydraulic winning. Stoping operations are to be carried out simultaneously in two strips. Each strip must be mined successively in separate blocks. Each block is isolated by rows of concrete supports, which are erected along the dip and along the strike of the seam. After stoping operations in a block have been completed, the roof is allowed to settle. During roof settlement, the concrete supports located along the contour of the strip perform the function of an enclosing support. The concrete supports located within the worked-out space, before the roof settles, are either destroyed with the aid of explosives or must lose their ability to support the roof by removal of the wooden cribs. Coal broken from the stoping and development faces is transported by water along chutes into a so-called hydraulic chamber located at the main haulage drift, whence it is delivered by pumps through pipelines to the preparation plant.

Driving of preparatory and entry workings

Before the start of stoping operations, within the limits of the extraction field it is necessary to drive (Fig. 2) the following workings: main haulage drift 1, lower accumulating drift 2, lower cut-out raises 3, ventilation drift 4, upper accumulating drift 5, upper cut-out raises 6, crosscuts 7, chutes 8, and raises for erecting concrete supports 9.

The accumulating drifts are driven at the floor and roof of the seam and are accordingly called upper or lower accumulating drifts. From the accumulating drifts, cut-out raises are driven up the rise of the seam. The distance between the lower cut-out raises driven at the floor of the seam is taken as 7 m. The upper cut-out

Fig. 2. Mining system by strips along the dip with yielding concrete support

Visible drawing labels:

• No. I
• No. II
• Section G–G
• Section B–B

Visible dimensions and marks include: 7 m, 9 m, 10 m, 14 m, 20 m, 4.5 m, 0.5 m, 6 m, 5 m, and numbered elements 1–9.

workings are driven at the roof of the seam at intervals of 7 and 14 m, alternately, as shown in Fig. 2. Crosscuts, niches, and rising workings for erecting concrete supports are driven as the upper and lower slicing faces advance. The distance between crosscuts is 20 m; between niches and rising workings, not more than 4.5 m.

For driving preparatory and slicing workings, combines or drilling-and-blasting operations are used, with gravity hydraulic transport of the broken coal. As the faces advance, the pressure water line and metal chutes are extended. To ensure gravity hydraulic transport of coal, the workings are given a gradient of 3°–4°.

Erection of Concrete Supports

A number of research and design works have been devoted to the question of using concrete for supporting extraction workings. The designs proposed, for the room-and-pillar and shield systems of mining, carrying out preliminary extraction between inter-room and inter-shield pillars, followed by filling of the mined-out space with cemented backfill. For the first time in Kuzbass, such a design was proposed by mining engineer I. N. Kaznin in 1937 for the room-and-pillar system of mining. Industrial tests of this proposal were carried out considerably later, in 1947, at mine No. 3—3-bis in the Prokopyevsk district of Kuzbass [1, 2].

In subsequent years the idea of replacing coal pillars by strips or pillars of concrete backfill was developed by G. A. Lomov, N. A. Chikalo, V. F. Parusimov, B. M. Skoryi, and others [3, 4, 5]. Of considerable interest are the projects for the use of concrete backfill and cemented backfill prepared by the institutes VUGI and Unipromed, as well as the experimental work carried out at mines in Canada and Finland [4, 6].

When applying the proposed mining system, it is recommended to erect not continuous concrete pillars, but rows of concrete supports with wooden cribs at the roof of the seam. The cross-sectional dimensions of the concrete supports are 1.5 × 1.5 m. When rising workings are driven with the use of drilling-and-boring machines, the concrete supports have a circular section 1.5 m in diameter. The erection of concrete supports under underground conditions has not yet been sufficiently studied with regard to the use of industrial methods for transporting concrete through mine workings.

The authors of the present article, taking into account the experience of the Canadian Jeffrey asbestos mine [6], as well as the long-standing practice of constructing large hydraulic-engineering structures in the USSR, propose the following scheme for transporting concrete for the erection of supports:

1) concrete prepared on the surface is delivered through boreholes or shafts into receiving bunkers located within the extraction field;

2) transport of concrete from the receiving bunkers to the place where it is to be placed is carried out through pipes by means of concrete pumps;

3) the receiving bunkers are arranged within the extraction field at distances from one another, along the strike, of not more than 100–150 m, and along the dip, not more than 150–200 m.

Such a scheme for transporting concrete is, in our opinion, the most effective at a comparatively small depth of mining operations.

Extraction Work

Coal breaking in the extraction face, as indicated above, is carried out by drilling-and-blasting operations with subsequent use of hyd-

hydrotransport. The blastholes are drilled from workings located at the roof and the floor of the seam. For drilling blastholes from workings located at the roof of the seam, a PBS-110 machine is used. In workings located at the floor of the seam, blastholes are drilled with hand electric drills. The layout of the blastholes is shown in Fig. 2. Such an arrangement of the blastholes should ensure that, after the charges are blasted in the coal mass, a caving arch is formed that does not extend beyond the thickness of the coal seam. After the broken coal is removed by a jet of water, the coal pillars supporting the arch are destroyed by hydrobreaking. The advance of the extraction face per blasting operation is designed to be 2 m.

The spacing of the stowing, taken as 20 m, is determined by the distance between the rows of concrete supports installed along the strike of the seam. In some cases, in order to accelerate caving of the roof rocks, it will probably be necessary to use drilling-and-blasting operations. In this case the blastholes may be drilled from workings located at the roof of the seam.

Technical-and-economic indicators

The calculated technical-and-economic indicators of the mining system with strips along the dip and with yielding concrete support are given in Table 1.

Table 1

*) Actual indicators achieved at the “Polysaevskaya—Severnaya” mine of the “Kuzbassugol” combine in 1954–1955.

²) Actual indicators achieved at the “Siersza” mine (Poland).

In the calculations, the actual indicators of hydraulic sections in Kuzbass and in the Polish People’s Republic were taken into account. In particular, the indicators of the hydraulic section of the Polish mine “Silesia,” where a room-and-pillar system with hydraulic coal extraction is used, were taken as a basis. The section works a gently dipping seam with a thickness of 5 m.

It is evident from Table 1 that the system of mining by strips along the dip with yielding concrete support has higher technical-and-economic indicators in comparison with the system of mining by inclined slices with caving. In particular, it is characterized by high productivity, greater safety in coal-extraction operations, low consumption of timber materials, and conditions ensuring wide application of hydromechanization.

REFERENCES

1. Stelmakh N. M. A room system of mining with concrete support by engineer I. N. Kaznin. Ugletekhizdat, 1948.

2. Proskurin V. V. The Prokopyevsk Mine of Kuzbass. Tomsk; Poligrafizdat, 1951.

3. Chinakal N. A. A shield system of mining for lower horizons with complete stowing in the mining of thick steeply dipping seams. Problems of Mining (on the 75th anniversary of Academician A. M. Terpigorev). Ugletekhizdat, 1948.

4. Improvement of methods for mining thick seams of Kuzbass with stowing. Ugletekhizdat, 1956.

5. Improvement of the shield mining system. Ugletekhizdat, 1954.

6. Kharakhonichev V. P. Replacement of ore interchamber pillars by concrete pillars. Mining Journal, No. 6, 1957.